GB1233992A - - Google Patents

Abstract

1,233,992. Strapping tools. SIGNODE CORP. 7 March, 1969 [3 June, 1968], No. 12136/69. Heading F2G. A pneumatically operable strapping tool comprises an air operated motor M for progressively applying and maintaining tension to the strapping, an air supply line 25 leading to the motor M, sealing instrumentalities effective when actuated to seal the overlapping end portions of the tensioned strapping, and pneumatic means responsive to a predetermined back-up pressure in the supply line 25 for actuating the sealing instrumentalities. In the construction shown the tensioning is effected through a feed wheel 54 and a back-up pad 56 on the frame of the tool. Before the start of a strap tensioning and sealing cycle the motor M is held in an inoperative position by a latch arm 58, this arm 58 being unlatched by a plunger 62 on the operation of a tensioning valve TV by a start lever 160. The tensioning valve is then held in its operative position by a latch member 170 and supplies air to the tensioning motor M. Air is also supplied to the inlet of a sealing valve SV. The pneumatic means comprise a pressure relief valve PRV connected to the supply line 25 and actuated by back-up pressure on a diaphragm 220 against spring loading, a trip release valve TRV actuated by the pressure relief valve through a trip finger 244, air thereby passing through the trip release valve TRV to a sealing control cylinder 209. A plunger 208 working in the cylinder actuates the sealing valve SV to allow air at the inlet thereof to pass to a sealing cylinder 74. The sealing valve SV is latched in its operative position by an extension 214 on a latch shaft 210 and is unlatched when a piston 106 in the sealing cylinder 74 reaches the end of its operative stroke and engages an extension 218 also on the latch shaft 210. The latch member 170 is freed from the tensioning valve TV to allow the valve to return to its inoperative position by the plunger 208 engaging a cam wing 184 of the latch member 170. The piston 106 operates a pair of crimping jaws 122 to crimp a metal seal S about the overlapped ends of the strapping through toggle links. The seals S are fed one at a time to the crimping jaws from a magazine (32, Fig. 1, not shown). The sealing may be effected by a heat sealing process actuated by operation of the sealing control cylinder.